1. Field of the Invention
The present invention relates to a lamp driver, and more particularly, to a lamp driver controlling driving power being supplied to a lamp to suppress a transient state thereof, depending on a first comparison result signal obtained by comparing a current sensing signal sensing a current flowing through the lamp according to the on/off state of a dimming signal with a reference signal set beforehand, or on a second comparison result signal set beforehand.
2. Description of the Related Art
With the advent of the information age, the demand for a high performance display capable of presenting information in various formats such as images, graphics and text for the rapid transmission thereof has been rapidly increasing. In order to meet the demand, the display industry is undergoing rapid growth.
Particularly, a Liquid Crystal Display (LCD) has been greatly improved as a next-generation high-tech display device in recent years since it has low power consumption and is relatively thin and lightweight as compared with a cathode ray tube (CRT). The LCD has been widely used in an electronic watch, an electronic calculator, a computer, a television and the like.
Meanwhile, the LCD includes a liquid crystal panel displaying an image and a backlight unit supplying light to the liquid crystal panel.
The liquid crystal panel has a thin-film transistor substrate including a gate line, a data line, a thin-film transistor, a pixel electrode and the like, and a color filter substrate including a color filter, a common electrode and the like. When a pixel voltage is applied to the liquid crystal panel, the liquid crystal panel is driven to adjust the transmittance of the light supplied by the backlight unit so that it can display an image.
A fluorescent lamp, a light emitting diode (LED) or the like is used as the backlight unit. In recent years, the LED allowing for low power consumption and superior color reproduction has been used a lot as the backlight unit.
Meanwhile, such an LCD uses a dimming control method to adjust screen brightness through the brightness control of the backlight unit, i.e., the fluorescent lamp or the LED. A control signal used in the dimming control method employs a Pulse Width Modulation (PWM) method to control the amount of power supplied to the fluorescent lamp or the LED according to duty of the control signal to thereby adjust brightness.
Meanwhile, power is supplied to the fluorescent lamp or the LED through the conversion of input power based on a feedback signal of the current flowing through the fluorescent lamp or the LED. At this time, when a dimming control signal having a preset duty ratio or less is inputted, the voltage level of the feedback signal becomes lower than a reference level, so that a switching IC employed in a power conversion circuit may stop its switching operation.
However, the duty of the dimming control signal may be minimized instantaneously and then provided normally. In this case, the switching IC detects a feedback signal having a voltage level lower than the reference level and stops power supply. Thereafter, when the duty of the dimming control signal is provided normally, the switching IC restarts power supply. At this time, power is to be in a transient state instantaneously so that a flicker may be caused.